Symptoms: Machine wouldn’t boot and had switch matrix problems once it did boot.Location: Denver, CO

The pinball machine didn’t boot due to some oxidation on the ROM pins. I removed the game ROM from the MPU and cleaned with contact cleaner.

Once the game booted, there were solenoids firing in attract mode which usually indicates that there are some switch matrix problems. The diagnostics revealed that many of the opto switches were not working.

On many Williams machines of this era, there is a board mounted under the playfield that provides an interface between the optical switches and the switch matrix. In the case of Indiana Jones, it’s labeled “10 Sw PCB”, which will interface up to 10 optical switches.

I began to take some voltage measurements on this board and nothing was correct. Upon closer examination, something acidic had dripped on the board and, just like battery alkaline, had eaten through the circuit board traces. At first I couldn’t find the source of this acid, but eventually figured out it was from the electrolytic capacitor (C1) that was also located on the board.

Capacitor C1 had leaked, damaging the area around D13 and U3.

I cleaned up the board and replaced C1 and U3. I had to re-wire some of the circuit traces since some no longer had continuity. I reconnected the board and switch matrix worked fine.

In testing the machine, I found a blown fuse associated with the flash bulbs. I replaced the fuse and checked the flasher sockets and found a frayed wire that probably had caused the fuse to blow.

This same customer also had a The Machine: Bride of PinBot (Williams, 1991) that he wanted me to take a look at.

The first thing I noticed was that the lights weren’t sequencing properly around the “helmet”, plus some of the bulbs appeared to be out. After tracing signals to the Chase Light interface board, I found some wiring errors that were probably made at the factory. And the problems with non-working bulbs was related to connection issues. Once repaired, the lights sequenced properly around the helmet.

When playing the game I noticed the slingshots were making the sound like they were firing, but they weren’t actually kicking the ball. A peak under the playfield revealed that both plunger/link assemblies were broken.

Broken links associated with slingshots.

I replaced both of those plunger/link assemblies and the machine played well.

I’d like to note that I stock a lot of parts so that I don’t have to make multiple trips to a customer’s location. While I can’t stock an entire warehouse, I had all of the parts on-hand to repair both of these machines, including the circuit board, in a single visit.

Reviews

"Randy is a true professional with amazing knowledge of electrical wiring, programming, boards and mechanical workings. He has always arrived promptly with all the tools and parts needed to efficiently complete the jobs. Randy has worked on my three Williams machines (Taxi, T2, and Funhouse) and based on his previous work, I am confident he could solve any future issue." --Greg M., Louisville, CO

"Randy was there an hour and found the problem and also a couple other potential issues. He was very professional and knowledgeable and I feel he has the ability to troubleshoot anything pinball or anything electronic for that matter." --Craig H., Broomfield, CO

"Randy just left here and after over 20 years I now have a jukebox that works."--Jeff, Aurora, CO.

"Randy is always very professional and extremely knowledgeable about the work that needs to be done. He is the best out there that can be found for pinball and juke box repairs."--Larry, Sidney, NE.